Six more.
Some aren't what they look like.

Water ingress. The breather was pointing straight up under a daily 60 bar washdown, so water got pulled in every time the hot box cooled and the air inside contracted. Emulsified oil loses its film in weeks and the worm and seal go with it.

The tell: milky, foamed oil, not just dark. Dark oil is age. Milky is water.

Fix: turn the breather down or fit a desiccant breather, change the oil, done.

Side loading. The rod is scored down one side only and polished clean on the other, and the foot mount is twisted out of square. The rod is being dragged against the bearing on every stroke. Three kits in and nobody looked past the seals at the bracket.

The tell: scoring on one face of the rod only. Even wear is air or age. One-sided wear is alignment.

Fix: shim the mount true, or fit a floating joint. Then the seals last.

Single phasing. A genuine overload cooks all three phases evenly. Two burnt and one clean means the motor lost a phase and kept trying to run on two, dumping the load into those windings. The fault is upstream, a failed contactor pole or a blown fuse, not the motor.

The tell: uneven burn. Two dead, one clean copper.

Fix the cause first. Fit a new motor without finding the lost phase and you'll cook that one too.

The sprocket. Look at the teeth, they're hooked into shark fins. A worn sprocket chews a new chain to death in weeks because the pitch no longer matches. Chain and sprockets wear as a set and get replaced as a set.

The tell: hooked, asymmetric teeth on a bright new chain.

Fix: replace the sprockets with the chain, every time.

Sunlight. There's a goods-out shutter door on the sightline, and at about 2pm on a clear day the sun drops to the angle where it pours straight down the beam into the receiver and blinds it. That's why it never happens on nights and never in the rain. Nobody plots the faults against the clock and the weather, so it gets chased as an electrical fault for months.

The tell: it's tied to time of day and sky, not to the line.

Fix: a shroud, a polarised sensor, or turn it to face away from the door. Costs nothing.

Inductive kickback. There's a bare relay coil wired to that channel with no suppression diode. Every time the coil de-energises it throws a reverse voltage spike back at the output transistor, and eventually it cooks it. The card was never the fault.

The tell: one scorched channel next to clean ones, and a coil with nothing across it.

Fix: a flyback diode across the coil. About 20p. Not a third card.